1. Field of the Invention
The present invention relates to an apparatus, for example, a camera, an image-reading apparatus, and the like capable of operating in cooperation with a film cartridge accommodating a film having a magnetic-recording region formed thereon to read an information on the region.
2. Description of the Related Art
In recent years, film cartridges accommodating a film having a magnetic-recording region formed thereon have been proposed. As apparatuses which use this kind of film, a camera, an image-reading apparatus, and the like having a magnetic head for reading and writing magnetic information have been proposed. In these apparatuses, no information is recorded on the magnetic-recording region of the film before frames of the film are exposed, but when a photographing operation is executed, information corresponding to the image of an object photographed on each frame is recorded on the magnetic-recording region. The information includes data of a photographed date, photographic conditions (aperture value and shutter speed), the number of sheets on which images are printed, comments, and the like. Film cartridges having a function of displaying the state of a roll of film, for example, "unexposed", "partially exposed", and "exposed" have been also proposed.
In the image-reading apparatus, the data of a necessary number of sheets on which images are printed and images and photographed dates are displayed thereon, based on the information read in reproducing images. In the camera, photographic conditions or the like are recorded when a photographic operation is performed, and it is determined whether a frame has been exposed or is unexposed when a film cartridge accommodating a partially exposed roll of film is loaded into the camera and then, the film is wound so that exposure can be started with the first unexposed frame. Whether the frame has been exposed or is unexposed is determined according to whether magnetic information has been recorded on a magnetic-recording region of each frame, namely, according to whether the level of a signal reproduced from the magnetic-recording region is higher than a predetermined reference level.
But there is a possibility that the magnetic information cannot be read correctly if a data signal, corresponding to the magnetic signal, reproduced by the magnetic head includes noise generated due to the influence of a magnetic field or an electric field present outside the camera. For example, in determining whether a frame has been exposed or is unexposed, there is a possibility that the level of the noise is higher than the predetermined reference level. In this case, it is erroneously determined that the frame has been exposed although magnetic information has not been recorded on the magnetic-recording region for that frame. On the contrary, if the reference level is set to a higher level, on the assumption that a noise having a high level is generated outside the camera, there is a possibility that an exposed frame is erroneously identified as an unexposed frame and that the exposed frame is exposed again.